Date: 2017jul12 Update: 2025jan1 Product: Roundcube webmail OS: Linux Q. Roundcube: Connection to storage server failed. Server Error: Could not connect to localhost4:143: Connection refused Why? A. This worked for me. In file /etc/roundcubemail/config.inc.php I commented out the line specifying the IMAP vendor:

# $config['imap_vendor'] = 'dovecot';

And restarted Apache:

systemctl restart httpd

I am actually using Dovecot. But, perhaps, Roundcube is expecting Dovecot to behave in a non-standard way that it no longer does?